One aim of this project is to use transcranial magnetic stimulation (TMS) of the brain to study physiological changes in different behavioral states and disorders. Over the past year, we have obtained and published data from patients with obsessive-compulsive (OCD) disorder showing abnormally increased motor cortex excitability suggesting a defect in neural inhibition. This is consistent with current theories and functional brain imaging data, but is the first direct neurophysiological evidence. Preliminary data also suggests that this condition may be present to a lesser degree in individuals without the disorder, but with similar traits. We have also shown that some of the same parameters of motor cortex function vary with the menstrual cycle in normal women as a result of hormone effects on the GABA-A receptor. We hope that these data will lead to better treatments for menstrual-related disorders such as depression and epilepsy. The other major project goal is to develop TMS as a means of altering cortical function in order to treat some of the same disorders and to study the localization of cognitive functions such as language, memory, and calculation. Current work combines repetitive TMS with blood flow PET imaging to detect how and where TMS induces changes in brain activity. We have completed a study in normal volunteers showing strong positive and negative correlations of brain activity with the strength of the stimulation. These studies will help us and others using brain stimulation to treat and investigate psychiatric and neurological disorders. - neurophysiology, brain stimulation, motor cortex, normal volunteers, neurological disorders, psychiatric disorders - Human Subjects